Conductive elastomer materials are used to form gaskets for sealing electronic modules which are typically enclosed in a rigid enclosure. The gaskets provide physical integrity by preventing unwanted materials from entering the enclosure. The gaskets are also provided to further radio frequency (rf) signal shielding to prevent unwanted emission of signals from within the module and to prevent unwanted reception of radio frequency signals from entering the module. Where rf shielding is of concern, it is highly desirable that the gasket be electrically conductive. To provide a good physical seal, the gasket is desirably of a flexible material such as an elastomer.
Conductivity has been imparted to elastomer materials by mixing finely divided conductive particles, usually metallic, with the materials that are cast to provide the conductive elastomer. The mixture is typically cast as a sheet from which gasket shapes are then cut. There are disadvantages associated with such conductive elastomer gaskets, including poor conductivity and poor thermal cycling behavior. The poor conductivity occurs as a result of several factors, including the fact that inter-particle contact is required for the material as a whole to be conductive and achieving such inter-particle contact over the continuum of the gasket is difficult to achieve. Additionally the conductive particle loading of the elastomer material may be inadequate either overall or in localized areas. Also, such gaskets may likewise have relatively poor thermal cycling behavior of the conductivity because the particles may not stay in continuous conductive contact as the material is heated and cooled.
Poor or variable (e.g., with thermal cycling) conductivity results in sporadic and/or inadequate electronic shielding of the equipment using such conductive elastomer material for rf gaskets. This may lead to failure to meet specifications and/or inappropriate electrical performance.
Various methods have been attempted in the past to deposit metal layers on non-metallic and insulating substrates, however, none of the prior approaches have produced conductive layers on flexible materials which retain adherence to the flexible material and continuity after flexing of the material.